Plasma processing apparatus and plasma processing method

Abstract

An optimum application voltage for reducing deposits on a peripheral portion of a substrate as well as improving a process result in balance is effectively found without changing a height of a focus ring. A plasma processing apparatus includes a focus ring which includes a dielectric ring provided so as to surround a substrate mounting portion of a mounting table and a conductive ring provided on the dielectric ring; a voltage sensor configured to detect a floating voltage of the conductive ring; a DC power supply configured to apply a DC voltage to the conductive ring. An optimum voltage to be applied to the conductive ring is obtained based on a floating voltage actually detected from the conductive ring, and the optimum application voltage is adjusted based on a variation in the actually detected floating voltage for each plasma process.

What is claimed is: 
     
       1. A plasma processing method for performing a plasma process on a substrate in a plasma processing apparatus which includes a mounting table for mounting thereon the substrate and a focus ring provided on the mounting table so as to surround the substrate,
 wherein the focus ring includes a dielectric ring provided so as to surround a substrate mounting portion of the mounting table and a conductive ring provided on the dielectric ring, 
 the conductive ring is connected with a voltage sensor for detecting a floating voltage thereof and a DC power supply for applying a DC voltage thereto, 
 the conductive ring includes an outer ring and an inner ring as one body, the outer ring being provided so as to surround a peripheral portion of the substrate and having a top surface higher than the substrate mounted on the substrate mounting portion, and the inner ring extending inwardly from the outer ring so as to be positioned under the peripheral portion of the substrate and having a top surface lower than the substrate, 
 further wherein the plasma processing method comprises: 
 obtaining an optimum application voltage value to be applied to the conductive ring based on a floating voltage of the conductive ring detected by the voltage sensor and storing the obtained optimum application voltage value in a storage; 
 when a plasma process is performed, detecting a floating voltage of the conductive ring by the voltage sensor for each plasma process, obtaining a variation of the floating voltage, and adjusting the optimum application voltage value stored in the storage based on the variation in the floating voltage; and 
 performing the plasma process on the substrate by applying a voltage corresponding to the adjusted optimum application voltage value to the conductive ring from the DC power supply. 
 
     
     
       2. The plasma processing method of  claim 1 , wherein the outer ring is divided into an outer peripheral portion and an inner peripheral portion,
 the inner peripheral portion is electrically connected with the inner ring and the outer peripheral portion is electrically insulated from the inner peripheral portion and the inner ring, and 
 the DC power supply and the voltage sensor are connected with the inner peripheral portion or the inner ring. 
 
     
     
       3. The plasma processing method of  claim 1 , further comprising:
 if it is allowed to select one among a plurality of plasma process conditions, obtaining an optimum application voltage value to be applied to the conductive ring based on a floating voltage of the conductive ring detected by the voltage sensor for each of the plasma process conditions and storing the obtained optimum application voltage value in the storage; 
 when a plasma process is performed under the selected plasma process condition, detecting a floating voltage of the conductive ring by the voltage sensor for each plasma process, obtaining a variation of the floating voltage, and adjusting the optimum application voltage value stored in the storage and related to the selected plasma process condition based on the variation in the floating voltage; and 
 performing the plasma process on the substrate under the plasma process condition by applying a voltage corresponding to the adjusted optimum application voltage value to the conductive ring from the DC power supply. 
 
     
     
       4. The plasma processing method of  claim 3 , wherein the outer ring is divided into an outer peripheral portion and an inner peripheral portion,
 the inner peripheral portion is electrically connected with the inner ring and the outer peripheral portion is electrically insulated from the inner peripheral portion and the inner ring, and 
 the DC power supply and the voltage sensor are connected with the inner peripheral portion or the inner ring. 
 
     
     
       5. The plasma processing method of  claim 1 , wherein the optimum application voltage value is most suitable to increase both an effect of reducing deposits on the peripheral portion of the substrate and an improvement in a process result. 
     
     
       6. The plasma processing method of  claim 3 , wherein the optimum application voltage value is most suitable to increase both an effect of reducing deposits on the peripheral portion of the substrate and an improvement in a process result. 
     
     
       7. The plasma processing method of  claim 5 , wherein the outer ring is divided into an outer peripheral portion and an inner peripheral portion,
 the inner peripheral portion is electrically connected with the inner ring and the outer peripheral portion is electrically insulated from the inner peripheral portion and the inner ring, and 
 the DC power supply and the voltage sensor are connected with the inner peripheral portion or the inner ring. 
 
     
     
       8. A plasma processing method for performing a plasma process on a substrate in a plasma processing apparatus which includes a mounting table for mounting thereon the substrate and a focus ring provided on the mounting table so as to surround the substrate,
 wherein the focus ring includes a dielectric ring provided so as to surround a substrate mounting portion of the mounting table and a conductive ring provided on the dielectric ring, 
 the conductive ring includes an outer ring and an inner ring as separate bodies, the outer ring being provided so as to surround a peripheral portion of the substrate and having a top surface higher than the substrate mounted on the substrate mounting portion, and the inner ring being spaced apart inwardly from the outer ring so as to be positioned under the peripheral portion of the substrate and having a top surface lower than the substrate, and 
 the outer ring and the inner ring are connected with a DC power supply for the outer ring and a DC power supply for the inner ring, respectively, and the outer ring is connected with a voltage sensor for detecting a floating voltage thereof, 
 further wherein the plasma processing method comprises: 
 obtaining an optimum application voltage value to be applied to the outer ring based on a floating voltage of the outer ring detected by the voltage sensor and an optimum application voltage value to be applied to the inner ring, and storing the obtained optimum application voltage values in a storage; 
 when a plasma process is performed, detecting a floating voltage of the outer ring by the voltage sensor for each plasma process, obtaining a variation in the floating voltage, and adjusting the optimum application voltage value of the outer ring stored in the storage based on the variation in the floating voltage; and 
 performing the plasma process on the substrate by applying a voltage corresponding to the adjusted optimum application voltage value of the outer ring to the outer ring from the DC power supply for the outer ring and by applying a voltage corresponding to the optimum application voltage value of the inner ring stored in the storage to the inner ring from the DC power supply for the inner ring. 
 
     
     
       9. The plasma processing method of  claim 8 , wherein the outer ring is divided into an outer peripheral portion and an inner peripheral portion,
 the inner peripheral portion is electrically insulated from the inner ring and the outer peripheral portion is electrically insulated from the inner peripheral portion and the inner ring, and 
 the DC power supply for the outer ring and the voltage sensor are connected with the inner peripheral portion. 
 
     
     
       10. The plasma processing method of  claim 8 , wherein the optimum application voltage value is most suitable to increase both an effect of reducing deposits on the peripheral portion of the substrate and an improvement in a process result. 
     
     
       11. The plasma processing method of  claim 10 , wherein the outer ring is divided into an outer peripheral portion and an inner peripheral portion,
 the inner peripheral portion is electrically insulated from the inner ring and the outer peripheral portion is electrically insulated from the inner peripheral portion and the inner ring, and 
 the DC power supply for the outer ring and the voltage sensor are connected with the inner peripheral portion. 
 
     
     
       12. The plasma processing method of  claim 8 , further comprising:
 if it is allowed to select one among a plurality of plasma process conditions, obtaining an optimum application voltage value to be applied to the outer ring based on a floating voltage of the outer ring detected by the voltage sensor for each of the plasma process conditions, obtaining an optimum application voltage value to be applied to the inner ring for each of the plasma process conditions, and storing the obtained optimum application voltage values in the storage; 
 when a plasma process is performed, detecting a floating voltage of the outer ring by the voltage sensor under the selected plasma process condition, obtaining a variation of the floating voltage, and adjusting the optimum application voltage value of the outer ring stored in the storage and related to the selected plasma process condition based on the variation in the floating voltage; and 
 performing the plasma process on the substrate by applying a voltage corresponding to the adjusted optimum application voltage value of the outer ring to the outer ring from the DC power supply for the outer ring and by applying a voltage corresponding to the optimum application voltage value of the inner ring stored in the storage and related to the selected plasma process condition to the inner ring from the DC power supply for the inner ring. 
 
     
     
       13. The plasma processing method of  claim 12 , wherein the optimum application voltage value is most suitable to increase both an effect of reducing deposits on the peripheral portion of the substrate and an improvement in a process result. 
     
     
       14. The plasma processing method of  claim 12 , wherein the outer ring is divided into an outer peripheral portion and an inner peripheral portion,
 the inner peripheral portion is electrically insulated from the inner ring and the outer peripheral portion is electrically insulated from the inner peripheral portion and the inner ring, and 
 the DC power supply for the outer ring and the voltage sensor are connected with the inner peripheral portion.